In recent years, there has been growing concern to produce energy-efficient lubricated components. Moreover, modern engine oil specifications require lubricants to demonstrate fuel efficiency in standardized engine tests. The thickness and frictional characteristics of lubricant films are known to affect the fuel economy properties of oils.
When rubbing surfaces in a machine (engine, gear system or transmission) come into contact, a frictional force exists that retards the motion of the surfaces. This frictional force, called boundary friction, reduces the efficiency of the machine. Boundary friction coefficients may be measured for a lubricant composition using the high frequency reciprocating rig (HFRR). The boundary friction measured in the HFRR is known to be related to fuel efficiency in vehicles. The ability of the lubricant composition to reduce boundary layer friction is reflected by the determined boundary lubrication regime coefficient of friction (COF). A lower value is indicative of lower friction and thus improved fuel economy.
The present disclosure relates to a lubricant composition, method for reducing a boundary friction coefficient of a lubricant composition, and method for improving fuel economy. The lubricating oil composition includes a base oil, a) a metal-containing phosphorus antiwear compound in an amount sufficient to provide from about 100 to about 1000 ppm by weight phosphorus based on a total weight of the lubricant composition, and b) an oxygen-polymerized vegetable oil, different from the base oil. The base oil is present in the lubricant composition in an amount from about 50 wt. % to about 99 wt. % based on the total weight of the lubricating oil composition.
Another embodiment of the disclosure provides a method for reducing a boundary friction coefficient of a lubricating oil composition. The method includes lubricating an engine with the lubricating oil composition comprising a base oil, a) a metal-containing phosphorus antiwear compound in an amount sufficient to provide from about 100 to about 1000 ppm by weight phosphorus based on a total weight of the lubricant composition, and b) an oxygen-polymerized vegetable oil, different from the base oil. The base oil is present in the lubricating oil composition in an amount from about 50 wt. % to about 99 wt. % based on the total weight of the lubricating oil composition.
Yet another embodiment of the disclosure provides a method for improving the fuel economy of a vehicle including lubricating the engine of the vehicle with a lubricating oil composition that includes a base oil, a) a metal-containing phosphorus antiwear compound in an amount sufficient to provide from about 100 to about 1000 ppm by weight phosphorus based on a total weight of the lubricant composition, and b) an oxygen-polymerized vegetable oil, different from the base oil. The base oil is present in the lubricating oil composition an amount from about 50 wt. % to about 99 wt. % based on the total weight of the lubricating oil composition.
In some embodiments, the amount of oxygen-polymerized vegetable oil in the lubricant additive is sufficient to provide from about 0.1 to about 2.0 wt. %, such as from about 0.2 to about 1.0 wt. % oxygen-polymerized vegetable oil based on a total weight of a lubricant composition containing the additive.
In some embodiments, the oxygen-polymerized vegetable oil has a number average molecular weight ranging from about 500 to about 5,000 Daltons and a polydispersity (Mn/Mw) ranging from about 1.2 to about 3.5.
In some embodiments the metal-containing phosphorus antiwear compound includes a mixture of (A) a metal-containing phosphorus antiwear compound derived from primary alcohols and (B) a metal-containing phosphorus antiwear compound derived from secondary alcohols, wherein a weight ratio of (A) to (B) based on ppm by weight phosphorus provided by (A) and (B) to the lubricant composition ranges from 0:1 to about 4:1. In other embodiments, the metal-containing phosphorus antiwear compound is derived from a mixture of primary and secondary alcohols. In other embodiments, the metal-containing phosphorus antiwear compound is present in an amount sufficient to provide a lubricant composition with from about 200 to about 800 ppm by weight phosphorus based on a total weight of the lubricant composition.
In some embodiments, a lubricant composition contains a base oil and from about 2 wt. % to about 12 wt. % of a lubricant additive containing the metal-containing phosphorus antiwear compound and the oxygen-polymerized vegetable oil, based on a total weight of the lubricant composition.
In some embodiments, the base oil is present in the lubricant composition in an amount ranging from about 50 wt. % to about 99 wt. % based on the total weight of the lubricant composition.
An unexpected advantage of the additive and methods described herein is that the boundary coefficient of friction is reduced by the combination of metal-containing phosphorus antiwear compound and oxygen-polymerized vegetable oil so that the boundary coefficient is synergistically lower than provided by the metal-containing phosphorus antiwear compound in the absence of the oxygen-polymerized vegetable oil or the oxygen-polymerized vegetable oil in the absence of the metal-containing phosphorus antiwear compound. It was also unexpected that the oxygen-polymerized vegetable oil, at such a low concentration in the base oil, in combination with metal-containing phosphorus antiwear compound would provide a synergistic decrease in the boundary coefficient of friction. Typical compositions containing vegetable oils contain much more than 10 wt. % of the vegetable oil component.